Jan 25, 2013 by Brian Wallheimer

(Phys.org)—Some types of carbon nanotubes used for strengthening plastics and other materials may have an adverse effect on soil microbiology and soil microbial processes, a Purdue University study shows.

Specifically, these raw, non-functionalized single-walled carbon nanotubes were shown to damage the active microbiology in low-organic soil. Ron Turco, a professor of agronomy, said many of the bacteria affected could be involved in carbon and nitrogen cycling, which are critical processes to ensure a fully functional soil.

"There appears to be more negative potential on the active microbial population than we thought," said Turco, whose findings were published in the journal Environmental Science & Technology. "The as-produced materials could be a negative environmental situation if they are released into low-organic soils that could not absorb them."

Functionalized carbon nanotubes have modifications that create chemical or biological changes to the nanotubes. They're often used in medicines, and Turco's research showed they had no effect in high-organic or low-organic soils.

Non-functionalized single-walled nanotubes - those lacking intentional surface alterations - are being added to a variety of products during manufacturing because they can strengthen the material without adding much weight. Nanotubes contained in manufacturing waste products may find their way into wastewater treatment plants and bio-solids that result from water purification. Those bio-solids cannot be released into water, so they are often discarded by spreading on land, adding critically needed plant nutrients to soil.

"Land application of biosolids is standard procedure now," Turco said. "If any of that contains nanotubes, that could be a problem."

Single-walled nanotubes also didn't affect microbes in high-organic soils, Turco said, likely because organic materials are highly reactive. Organic materials may have reacted with the nanotubes, leaving them unable to affect microbes.

"We want to alert people to the fact that if you're going to apply these as part of a land-treatment program, you may want to focus on high-organic matter soils," he said.

It's also possible, though much less likely, that nanotubes could contaminate soil through accidental spills during a delivery, Turco said.

Next, Turco said he would look at the effects on plants and soils from other nanomaterials and nanometals that are being more widely used in products for different properties they convey, such as nanosilver for its disinfecting properties and nanoindium, which is used in electronics.

AbstractThe use of single-wall carbon nanotubes (SWNTs) in manufacturing and biomedical applications is increasing at a rapid rate; however, data on the effects of a potential environmental release of the materials remain sparse. In this study, soils with either low or high organic matter contents as well as pure cultures of E. coli are challenged with either raw as-produced SWNTs (AP-SWNTs) or SWNTs functionalized with either polyethyleneglycol (PEG-SWNTs) or m-polyaminobenzene sulfonic acid (PABS-SWNTs). To mimic chronic exposure, the soil systems were challenged weekly for six weeks; microbial activities and community structures for both the prokaryote and eukaryote community were evaluated. Results show that repeated applications of AP-SWNTs can affect microbial community structures and induce minor changes in soil metabolic activity in the low organic matter systems. Toxicity of the three types of SWNTs was also assessed in liquid cultures using a bioluminescent E. coli-O157:H7 strain. Although decreases in light were detected in all treated samples, low light recovery following glucose addition in AP-SWNTs treatment and light absorption property of SWNTs particles suggest that AP-SWNTs suppressed metabolic activity of the E. coli, whereas the two functionalized SWNTs are less toxic. The metals released from the raw forms of SWNTs would not play a role in the effects seen in soil or the pure culture. We suggest that sorption to soil organic matter plays a controlling role in the soil microbiological responses to these nanomaterials.

Related Stories

Applying organic fertilizers, such as those resulting from composting, to agricultural land could increase the amount of carbon stored in these soils and contribute significantly to the reduction of greenhouse gas emissions, ...

(PhysOrg.com) -- Using an array of nanotube devices, each coated with a different organic material, researchers at the Israel Institute of Technology have developed diagnostic system that may be able to diagnose lung cancer ...

Semiconductor Research Corporation (SRC), SEMATECH and The University of Texas at Dallas researchers are the first to demonstrate that specific potentially hazardous organic contaminants present in a type of single-walled ...

Studies by U.S. Department of Agriculture (USDA) scientists indicate that organic farmers who need to periodically amend their soils with compost after planting can still control weeds -- and hold down costs -- by using fabric ...

Carbon nanotubes have many attractive properties, and their structure and areas of application can be compared with those of graphene, the material for whose discovery the most recent Nobel Prize was awarded. In order to ...

The latest DNA nanodevices created at the Technische Universitaet Muenchen (TUM)—including a robot with movable arms, a book that opens and closes, a switchable gear, and an actuator—may be intriguing ...

New types of membrane adsorbers remove unwanted particles from water and also, at the same time, dissolved substances such as the hormonally active bis-phenol A or toxic lead. To do this, researchers at the ...

The use of tiny drug-loaded nanocarriers for the safe, targeted delivery of drugs to designated parts of the body has received much press in recent years. Human trials of nanocarriers targeting pancreatic ...

User comments : 0

Please sign in to add a comment.
Registration is free, and takes less than a minute.
Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.